DIY Hydronic Floor Heating

[AC_Hacker]

Originally Posted by Daox

...do you have the 1st or 2nd edition of Modern Hydronic Heating for Residential and Light Commercial Buildings? The first edition is a bit cheaper some places, but I'd wonder how much updating has been done for the 2nd edition.

I have the 2nd edition. I've not seen the first edition. I'd imagine the basics of radiant heating don't change much. If there was a third edition, with greatly expanded information on heat pumps as the prime heat source, that would be a different story.

I've also read Hydronic Radiant Heating. It is like sitting in a chair by a fire with an experienced hydronics installer and learning hydronics lore and rules of thumb from a seasoned pro. I found it to be interesting and enjoyable to read, but it is not a design manual. If a local library has it, you should read it. If they don't have it, you might request it. It does contain lore that you can use to double check any designs you come up with. For instance, who would think that there could be potential problems with hydronics in bathrooms? Seems like the best place to start... Well, hydronic installations, if not done mindfully, can cause the wax toilet sealing ring to melt, which causes obvious problems. (Now that I've written this, I realize that I would recommend this book, as an adjunct to a more thorough book, but it is not a systematic design manual)

[AC_Hacker]

I have been considering Maxis' method of making a hydronic floor, by building it up, using layers of Sheetrock as the thermal mass material that is between rows of PEX piping. As I understand it, Maxis grouted the channel, under, around and over the PEX to insure maximum thermal conduction.

I like the idea for more than one reason...

• Lower weight of floor - Definitely a factor for me with my house that was built in 1892 (or earlier).
  
• Ease of installation - I haven't worked with cement much and the idea of pouring wet cement onto a floor sounds very challenging.
  
• Ease of un-installation - If results are not as positive as I would hope, I want to be able to return the floor to something that resembles its present state.

So, I have been considering the variables, and the physical and thermal characteristics of the mass material seems to me to be a variable worthy of attention.

I really like Maxis' idea of utilizing sheet rock that was left over from previous remodeling, it's a brilliant way to save money and material.

In my case, however I'll be buying my material new, so the choice of material is open. I tried to find values on-line of the thermal transmissivity, or K value. I found that the K values given in various product literature, varied all over the map, and it all made my brain start to ache.

So, I have been doing some initial testing of various wall-board and concrete board products. Here is a photo of my test setup...

This was all just thrown together, so I could get some idea if there was enough of a difference to even worry about.

I decided if there was a significant difference, I would refine my testing.

So the method I followed was to use a heat lamp as the heat source, placed the same distance from my test samples in all tests. The temperatures were measured each second by three thermistors placed 1 inch apart, using my DIY Datalogger. I ran each test for exactly 10 minutes using my Eco-Experimenter's Test Box. The readings for each measurement period were averaged together.

The ambient temperature was measured to be the same for all tests, my mini split does a good job of providing an even temperature. All of the test samples were stored in the same location (my living room), with 'breathing room' around each one. I kept the samples in this room for for four days, so that if there were any unusual temperature or humidity differences, they would even out.

So here I have a graph of the results so far...

This graph is useful only for ranking which material is a better thermal conductor than another, it is not useful for calculating how much better.

The horizontal axis is the "time' axis, the vertical axis is the temperature axis, no scale is implied, however, beginning temperatures were about 70 F and ending temperatures were as high as 145 F. The time duration of the test was about ten minutes. The time shown in the graphic is about eight minutes.

It is clear that in this test, Durock is the best conductor of heat then Wonderboard, and that Sheetrock (both white face and green face, anti mold) has the lowest thermal conductance of the materials tested.

I'll be repeating the tests, and adding other materials that seem appropriate.

Stay tuned...

-AC_Hacker

[Xringer]

I Googled "Durock thermal conductivity" and got some interesting hits.
It seems this is some good stuff for shielding your wood or pellet stove from walls
and floors containing wood.. Good to know. I may re-install my wood stove someday.

I was looking at a thin sheet of Durock a few weeks ago.. It was HEAVY stuff!
It felt like I was handling a sheet of solid concrete. It's some impressive material,
and I was wondering what it would do to my saw blades..

[Daox]

Originally Posted by AC_Hacker

I have the 2nd edition. I've not seen the first edition. I'd imagine the basics of radiant heating don't change much. If there was a third edition, with greatly expanded information on heat pumps as the prime heat source, that would be a different story.

Speaking of the 3rd edition. My wife was out shopping the other day and she knew I wanted this book, so she visited the local book store. Apparently, the 3rd edition is going to be coming out ~August of 2010. I'm currently planning on holding off on doing any floor work until some time after that.

[dremd]

Subscribed:
The In Floor PDF you linked to was SUPER informative!

One thing I'm still trying to figure out is pump sizing. I see the head through x feet of y pipe, but what I don't understand is what is a good flow rate.

[AC_Hacker]

Originally Posted by dremd

Subscribed:
The In Floor PDF you linked to was SUPER informative!

One thing I'm still trying to figure out is pump sizing. I see the head through x feet of y pipe, but what I don't understand is what is a good flow rate.

dremd,

I'm assuming that you're referring to this link?

http://www.radiantcompany.com/manual...l_web-2009.pdf

I'm still trying to work out the pump thing myself...

I know that it's in my hydronic book, but I haven't dug that deep yet.

So far, I know that if you pump fluid through a pipe, that there is a pumping rate where 'turbulent flow' begins. An it is desirable to pump fast enough to reach turbulent flow, because heat transfer is enhanced, and hard as it is to believe, power required is reduced.

The factors affecting the threshold of turbulent flow are:

• smoothness of pipe
• diameterr of pipe
• viscosity of fluid
• etc.

If you're gonna do some research, there is a mathematical construct called Reynolds number that is pivotal in calculating pump size.

There's probably a free program that will do this for you, or a Java Script page calculator that will do the trick.

Please share with us what you learn.


Best Regards,

-AC_Hacker

[dremd]

Originally Posted by AC_Hacker

dremd,

I'm assuming that you're referring to this link?

http://www.radiantcompany.com/manual...l_web-2009.pdf

Actually I was thinking about http://www.infloor.com/downloads/res...stallation.pdf
The radiant company one is good also, but the InFloor one was more at my level.


I've been reading everything *** Backwards, I thought that turbuant flow was to be avoided. Makes much more sense now.

[AC_Hacker]

dremd,

I added the 'Residential Design and Installation' to the first post of this thread.

Thanks,

-AC_Hacker

[AC_Hacker]

This post, originally by Maxis, is full of useful details of a radiant floor install he is doing in Latvia (if I remember correctly). He is retrofitting a house and interestingly is using three different approaches (different approach for each floor) in his retrofit. I have relocated this post here, since it is more relevant to radiant floors than to Homemade Heat Pumps.

To make his information more accessable, I have added units that should be more familiar to American readers. I may have been a bit heavy-handed in my conversions, so they should be viewed as 'ballpark' attempts, and not as engineering data.

-AC_Hacker

* * *

Originally Posted by Maxis

The first I should say that this will be the first winter with HP and radiant floors in my house. I could say something about results only after some time -when it will get colder.

Answers to your questions:
Quote:Originally Posted by AC_Hacker
A) Did the minimum bending radius of the PEX determine the pipe spacing? Did you use bending forms, or did you just allow the pipe to bend as it would and put concrete on top?

I have read that one meter of 20mm (3/4 in) pipe could give about 18W (61 BTU/hr) heat with standard temperatures. That means, if you put 5m/m2 (3/4 in. PEX, spaced 7 3/4 on center) than you will get about 90W (300 BTU/hr). In our area the heat loss range is from 60W to 150W per m2. I have used 16mm pipe and I put about 5 to 6m/m2 (5/8 PEX, spaced 6 1/2 in. to 7 3/4 in.) - I have not less than 15cm (6 in.) between pipes and then bending is not an issue - I didn't use any bending forms. Actually pipes should be put as spiral (not snake) and then you have only 90 degree bends. With spiral you also will get equal temperature in all room.

Quote:Originally Posted by AC_Hacker
C-1) How thick was your polystyrol (polystyrene? EPS?)? What kind of mesh did you put on top?

It was 75mm (3 in.) thick. The recommended thickness is 100mm (4 in.), but I had limitations and couldn't put more. The polyethylene film should be put on top to not allow concrate to flow between plates. Then I put 5mm (7/32 in.) (to be able to walk on it ) steel reinforcement mesh with 150 x 150 mm (6 x 6 in.) cells (than you don't have to measure the distance between pipes - just follow the mesh).


It is metal sheet used as roof or wall material. Look in pictures for details

The reinforcement mesh pieces was fixed to each other with special steel wire


As I said I could comment results after some time. But I have read thet there in Latvia it works fine.


Average temperatures C in my area in each month:
Jan -4.7 C (23.54 F)
Feb -4.3 C (24.26 F)
Mar -0.6 C (30.92 F)
Apr 5.1 C (41.18 F)
May 11.4 C (52.52 F)
Jun 15.4 C (59.72 F)
Jul 16.9 C (62.42 F)
Aug 16.2 C (61.16 F)
Sep 11.9 C (53.42 F)
Oct 7.2 C (44.96 F)
Nov 2.1 C (35.78 F)
Dec -2.3 C (27.86 F)

Possible minimum C in each month:
Jan -33.7 C (-28.66 F)
Feb -34.9 C (-30.82 F)
Mar -30.3 C (-22.54 F)
Apr -13.1 C (8.42 F)
May -5.5 C (22.1 F)
Jun -2.3 C (27.86 F)
Jul 4 C (39.2 F)
Aug 0 C (32 F)
Sep -4.1 C (24.62 F)
Oct -8.7 C (16.34 F)
Nov -18.9 C (-2.02 F)
Dec -31.9 C (-25.42 F)


Heating season = 203 days, average temperature 0,0 C (32 F)

Insulations:
Basement: 120mm polystyrol (4.75 in. EPS)
1st floor: walls are 210mm (8.25 in) logs - cutted from both sides + 50mm (2 in.)wood/concrete plates from outside
2nd floor - 200mm (7 7/8 in) rockwool


I didn't use this method, but there is different reflection materials, some are insulation + reflection sheet in one, some are just reflection material. There is the link to one page where you can find how to make it by yourself:
Solar Shed -- House Heating

Best regards
Maxis

[AC_Hacker]

Originally Posted by Maxis

The first I should say that this will be the first winter with HP and radiant floors in my house. I could say something about results only after some time -when it will get colder.

(...see full post above...)

Best regards
Maxis

So Maxis,

How is your hydronic floor heating project working for you?

Are you staying warm?

I'm very interested to know how it is performing for you.

I'll be starting my floor pretty soon.

Warm Regards,

-AC_Hacker